Driving system

Abstract

A driving system used for torque control is provided with: first and second speed sensors on first and second shafts; first output devices drivingly coupled to the first and second shaft; and an electronic control unit electrically connected to the first and second speed sensors and the first and second output devices and including a storage unit storing one or more values of differential torque ratios, the electronic control unit being configured to fetch a target torque value, determine a rotation speed difference, determine a sign from the determined difference and the target torque value, fetch one of the values from the storage unit, calculate from the fetched value and the determined sign a first distribution ratio, and perform control to cause the first and second output devices to output torques obtained by multiplying the calculated first distribution ratios by the target torque value.

What is claimed is: 
     
         1 . A driving system used for controlling torque output to a first shaft and a second shaft, comprising:
 a first speed sensor configured to measure a rotation speed of the first shaft;   a second speed sensor configured to measure a rotation speed of the second shaft;   a first output device drivingly coupled to the first shaft;   a second output device drivingly coupled to the second shaft; and   an electronic control unit electrically connected to the first and second speed sensors and the first and second output devices and including a storage unit storing one or more values of differential torque ratios, the electronic control unit being configured to fetch a target torque value, determine a difference in rotation speed of the first shaft from the second shaft, determine a sign from the determined difference in rotation speed and the target torque value, fetch one of the values from the storage unit, calculate from the fetched value and the determined sign a first distribution ratio in which the torque is to be distributed to the first shaft and a second distribution ratio in which the torque is to be distributed to the second shaft, and perform control to cause the first output device to output torque obtained by multiplying the calculated first distribution ratio by the target torque value and cause the second output device to output torque obtained by multiplying the calculated second distribution ratio by the target torque value.   
     
     
         2 . The driving system of  claim 1 , wherein the first output device includes a first electric motor electrically connected to the electronic control unit and a reduction gear set configured to transmit a rotation created by the first electric motor to the first shaft with reducing a speed of the rotation, and the second output device includes a second electric motor electrically connected to the electronic control unit and a reduction gear set configured to transmit a rotation created by the second electric motor to the second shaft with reducing a speed of the rotation. 
     
     
         3 . The driving system of  claim 1 , wherein the electronic control unit is configured to calculate the first distribution ratio on the basis of a formula 1/2 {1+k (TBR−1/TBR+1)}, and calculate the second distribution ratio on the basis of a formula 1/2 {1−k (TBR−1/TBR+1)}, where TBR represents the fetched value and k represents the determined sign. 
     
     
         4 . The driving system of  claim 1 , wherein the storage unit stores two or more values of the differential torque ratios and the electronic control unit is configured to select and fetch one of the values stored in accordance with a sign of the target torque value. 
     
     
         5 . The driving system of  claim 1 , wherein the electronic control unit is configured to adopt as the determined sign a sign of a result obtained by multiplying the target torque value by the determined difference in rotation speed.